1. Field
The disclosed concept pertains generally to current transformers and, more particularly, to current transformers for sensing current flowing in a conductor. The disclosed concept also generally pertains to energy monitoring systems for sensing current flowing in a conductor. The disclosed concept also generally pertains to methods for sensing current flowing in a conductor.
2. Background Information
Energy monitoring systems can monitor energy passing through one or more electrical conductors. A typical energy monitoring system includes one or more current transformers electrically connected to a base unit.
Current transformers of various types are generally known. Typically, a current transformer includes an annular iron core about which a plurality of turns of a number of windings are wrapped. In use, an electrical conductor is situated in the hole of the annular iron core, and when an alternating current is passed through the conductor, the conductor serves as a single turn primary winding to induce a current in the secondary winding. Depending upon the application, the secondary winding is electrically connected with a burden resistor of a base unit. The base unit senses a voltage across the burden resistor and responsively provides an output which may be, for instance, a measurement of the current. While current transformers and energy monitoring systems have been generally effective for their intended purposes, they have not been without limitation.
A dangerous or undesirable condition can arise when the secondary winding of the current transformer on an active primary load becomes open circuited. The open circuited condition may be caused by, for example, broken sensor wires between the current transformer and the base unit or unterminated sensor wires. The open circuited condition can cause the current transformer to output dangerous or undesirable voltage levels. Additionally, the open circuited condition prevents monitoring of the current of the active primary load.
In order to prevent the dangerous or undesirable voltage levels at the current transformer, a clamping circuit has been included in current transformers in order to limit the voltages levels at the current transformer. Although the clamping circuit prevents dangerous voltage levels at the current transformer, the open circuited condition will still prevent monitoring of the current of the active primary load.
The identification of the type and location of the error in the energy monitoring system requires the use of resources such as the time of a technician and/or the use of troubleshooting equipment. Moreover, in the case that the energy monitoring system includes a plurality of current transformers, troubleshooting resources are needed to even identify which one of the current transformers is not operating properly.
It thus would be desirable to provide an improved current transformer or energy monitoring system that overcome these and other shortcomings associated with the relevant art.